Checking on whether a Server is Serving
There are two web sites where you can get an indication of whether ATCS data are flowing from a certain server. One provides the information in tabular form; the other is shown on interactive regional maps. Both are the work of George Paine.
Tabular data by server
This ATCS Monitor Public Server Status lists all the servers that are shown in the ATCS Server Database and shows whether they have been active recently. The list is updated about once an hour via a brief probe to each server that notes whether it responds. Since the list is organized by server URLs, you need to know the URL of the server you are wondering about.
Server Status on your Smartphone or Tablet
The Server Status page can also be used to drive a desktop widget on your Android device; see these instructions.
Telemetry from the Code Line is a set of interactive coverage maps that display active CPs by showing colored flags along the rail routes. If a CP is shown as active (note the color-code legend below the maps), this means that at least some packets have been received during the course of the previous day.
To use the map, first select a region. You can then enlarge the map as needed to see the individual sites. Mousing over either the flags or the items in the MCP list will give you some information as to where they are.
Here's another way to have fun! Take a look at string lines, (also George's work), which show a distance-time analysis of train movements on selected rail lines using what some call string line diagrams, also known as Marey graphs or distance-time graphs.